What it is
Momentum is the empirical tendency for stocks that have outperformed over the past 6–12 months to keep outperforming over the next several months — and for laggards to keep lagging. It is a relative signal: you rank the whole universe by trailing return and lean toward the top.
The standard academic construction is "12-1" momentum: rank stocks by their trailing twelve-month price return, but skip the most recent month. The skip matters — over very short windows (days to a few weeks) stocks tend to reverse, not continue, so including last month pollutes the signal with short-term noise. Our production signal uses a stock's trailing 52-week price change as the momentum input.
Momentum = trailing 12-month price return (relative to the universe)
That is the whole idea. No earnings model, no discounted cash flow — momentum asks a single question: is this stock already winning?
Why it works
Momentum is not a quirk of one market or one decade. Jegadeesh and Titman documented it in U.S. stocks in 1993; it has since been found in nearly every equity market studied, in bonds, commodities, and currencies, and across more than a century of data. It is robust enough that Fama and French — long-time skeptics of anything beyond value and size — eventually acknowledged it as a distinct factor.
The leading explanations are behavioral:
- Under-reaction to news. When a company reports genuinely good news, the price often moves part of the way immediately and the rest over the following weeks as the market digests it. The drift is the momentum.
- Gradual information diffusion. Information spreads unevenly — funds, analysts, and retail investors learn at different speeds, so buying pressure arrives in waves rather than all at once.
- Herding and confirmation. Rising prices attract attention, attention attracts buyers, and the trend reinforces itself until something breaks it.
There is also a risk-based reading: momentum pays you for bearing the risk of sharp, occasional crashes (below). Whatever the mechanism, the effect has persisted for decades after publication — which is rare for a market anomaly and suggests it is structural, not a data-mining artifact.
What "good" looks like
There is no single threshold — momentum is relative — but rough intuition for a trailing-12-month figure:
- Negative: A laggard. Avoid for a momentum strategy, however cheap it looks.
- 0–20%: Roughly market-like. Not a momentum name.
- 20–60%: Genuine relative strength. The bulk of a momentum book lives here.
- Above 100%: A market leader in a powerful trend. These are the names momentum is built to ride — but they carry the most reversal risk, so position-sizing and diversification matter more, not less.
The signal is strongest when the move is broad and persistent — a steady year-long climb — rather than a single overnight gap on one headline.
Common gotchas
- Momentum crashes. This is the one that hurts. At sharp market turning points — March 2009, the most violent example — the prior losers rip higher and the prior winners get sold, so a naive momentum book can suffer a brutal, fast drawdown. Momentum's worst months are far worse than its best months are good. Any serious momentum strategy needs diversification and risk controls, not just a ranking.
- Junk rallies. Pure price momentum will happily buy a speculative, cash-burning stock that has tripled on a story. Some of those keep running; many round-trip to zero. Pairing momentum with a quality filter screens out the worst of this (see below).
- Turnover and costs. Momentum decays — a winner today may not be a winner in three months — so the strategy trades more than buy-and-hold. Transaction costs and taxes eat into the paper edge if you rebalance carelessly.
- Crowding. Momentum is well known, and when too much capital chases the same recent winners, the trade can become fragile. Concentration in a single hot theme is the warning sign.
How we use it
Momentum is the engine of our Momentum Leaders bucket — but we never run it naked. The selection works in two stages:
- A quality gate first. A name only qualifies if it is a real, durable business: roughly $2B+ in value, positive net income and free cash flow, double-digit return on equity, growing revenue, and a balance sheet that is not over-levered. This screens out the junk rallies before momentum ever sees them.
- Rank the survivors by 12-month momentum. Among quality businesses, the ones whose stocks are leading the market rise to the top.
We then apply a diversification cap — at most two names per broad sector — so the bucket can't collapse into a single hot theme, which is exactly where momentum is most prone to crashing. And because momentum is a forward bet, not a back-test artifact, every pick is logged at its pick-time price and tracked openly on our track record.
Bottom line
Momentum is the simplest durable edge in markets: winners tend to keep winning for a while. It is robust across centuries and asset classes, it is rooted in how slowly humans price new information — and it is dangerous precisely when markets turn, which is why it must be paired with quality and diversification rather than chased on its own. Buy strong businesses whose stocks are already working, size them sensibly, and respect the reversal risk.